Control of cross‐presentation during dendritic cell maturation
Gil‐Torregrosa BC., Lennon‐Duménil AM., Kessler B., Guermonprez P., Ploegh HL., Fruci D., Endert PV., Amigorena S.
AbstractThe initiation of most cytotoxic immune responses requires MHC class I‐restricted presentation of internalized antigens to CD8+ T lymphocytes, a process called cross‐presentation. In dendritic cells (DC), the only antigen‐presenting cells that activate naive T cells, cross‐presentation is particularly efficient after internalization of opsonized antigens or immune complexes, which are cross‐presented through a proteasome‐ and transporter associated with antigen processing (TAP)‐dependent MHC class I antigen presentation pathway. We now show that FcγR‐mediated cross‐presentation is tightly regulated during DC maturation. Cross‐presentation increases soon after activation by lipopolysaccharides, and it is then inhibited in fully mature cells. The initial induction of cross‐presentation results from an increase of both antigen internalization and delivery to the cytosol, and from a slight rise in the activity of the proteasome and TAP. The subsequent block of cross‐presentation in mature DC is a consequence of the selective down‐modulation of antigen internalization and cytosolic delivery, while proteasome and TAP activities continue to rise. Therefore, FcγR‐mediated cross‐presentation is regulated during DC maturation by the selective control of antigen internalization and transport to the cytosol.